Date: Tue, 24 Nov 2015 16:34:35 +0900
From: Namhyung Kim <namhyung@kernel.org>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
CC: Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Jiri Olsa <jolsa@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
        David Ahern <dsahern@gmail.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Subject: Re: [RFC/PATCH] perf tools: Introduce perf_thread for backtrace
Message-ID: <20151124073435.GD2636@sejong>
References: <1447999383-15456-1-git-send-email-namhyung@kernel.org>
 <20151123213936.GF10315@kernel.org>
MIME-Version: 1.0
In-Reply-To: <20151123213936.GF10315@kernel.org>
User-Agent: Mutt/1.5.24 (2015-08-30)
Content-Type: text/plain; charset="utf-8"
Content-Disposition: inline
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1647
Lines: 37

On Mon, Nov 23, 2015 at 06:39:36PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Fri, Nov 20, 2015 at 03:03:03PM +0900, Namhyung Kim escreveu:
> > Backtrace is a crucial info for debugging.  And upcoming refcnt
> > tracking facility also wants to use it.
> > 
> > So instead of relying on glibc's backtrace_symbols[_fd] which misses
> > some (static) functions , use our own symbol searching mechanism.  To
> > do that, add perf_thread global variable to keep its maps and symbols.
> > 
> > The backtrace output from TUI is changed like below.  (I made a key
> > action to generate a segfault for testing):
> 
> This is a really nice use of what we have, I guess we could simplify
> things further, not having to create a struct machine, as we have just
> one thread, and we're not interested in kernel addresses, so no need for
> kmaps, etc.

Yes, I thought about it.  But as adding the perf thread to an existing
machine can affect other thread(s), I didn't do it.  Maybe we can set
the perf threads' machine pointer in a hacky way without adding the
thread into the machine, but I'd rather not doing that too because
it's fragile and current code is simple enough IMHO.


> 
> But as-is it already looks better than what we were using :-)
> 
> I'll try testing it further and will probably switch to using it if
> nobody voices any problem we haven't realised with such approach.

Thank you!
Namhyung
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/